Nanopartiküllerin çevredeki davranış ve etkileri ile risk değerlendirmesi için yeni yaklaşımlar

Considering the needs for the Environmental Risk Assessment (ERA) of Engineered Nanoparticles (ENPs), the main aim of this PhD study is to propose an ERA approach for ENPs that enables evaluating all representative factors for the risk, provides tools for reducing uncertainties and points out further research needs and risk management strategies with quantitative risk communication. Silver nanoparticles (AgNPs) and TiO2 NP were chosen as model ENPs due to their common usage in consumer products. Two different AgNPs, with citrate and PVP coating, were used to compare the effects of coating material. In the context of this main aim, the following objectives were studied to generate data or knowledge for the proposed ERA: 1) to determine in a systematic manner the most relevant water chemistry parameters for the agglomeration of model ENPs, which is the key fate process for the fate of ENPs 2) to classify the aquatic environment based on the relevant water chemistry parameters for agglomeration by considering the possible temporal changes according to the results of ENP agglomeration behavior in natural water samples 3) to evaluate the toxicokinetics and toxicodynamics of AgNPs in E. crypticus by investigating the relation between uptake and effects and 4) to determine the survival and reproductive toxicity of AgNPs to E. crypticus and the relation between toxicity and soil organic matter content and pH of the soil. In the context of Chapter 2, selected anions, cations, natural organic matter (humic acid and fulvic acid) and synthetic organic compounds (sodium dodecyl sulphate and ethoxylates) that were commonly observed in surface water were tested for their effects on ENP agglomeration under environmentally realistic conditions. ENP agglomeration was characterized using the change in size as measured using dynamic light scattering and Nanosight Nanotrack. Then, the combinations of ions and natural organic matters were evaluated in terms of agglomeration behavior to compare with the specific effects and most related parameters with the agglomeration of selected compounds were determined as Ca2+/Mg2+ and dissolved organic matter concentrations in the aquatic medium. All of the agglomeration studies were conducted for 1 hour, 1 day and 1 week to assess ENP agglomeration changes over time depending on the type of ENP. A surface water simulated media in terms of agglomeration was proposed which was validated by comparison with natural surface water samples. Based on the results of Chapter 2, six surface water and three wastewater treatment plants were selected with different Ca2+/Mg2+ and dissolved organic matter concentrations to determine its effect on the change in ENP size. ENP agglomeration experiments were conducted in unfiltered and filtered samples to have environmentally realistic conditions. Agglomeration of citrate-coated AgNPs correlated well with Ca2+ concentration. However, dissolved organic carbon led to deviations at a certain concentration range. PVP-coated AgNPs were stable at their original size regardless of water chemistry. TiO2 NPs agglomerated up to micrometer scale in most of the water samples after 1 week. Correlation of their agglomeration behavior with Ca2+ concentration was weaker than that of citrate-coated AgNPs. However, the correlation improved when dissolved organic carbon content was higher than 2 mg/L. The effect of dissolved organic carbon on the stabilization of TiO2 NPs was more pronounced after 1 day. Fractionation of the samples based on molecular weight of the organic matter using ultrafiltration showed that agglomeration was much more pronounced for the fraction below 10 kDa than for unfiltered samples. Based on the correlations found, a classification scheme for the agglomeration of model ENPs in water over time was proposed. The uptake of AgNPs and AgNO3 in E. crypticus was followed for 10 days. A background solution with essential elements was spiked to inert quartz sand to prepare the exposure medium. E. crypticus were exposed to AgNPs at different dose levels for different times (2,3,5,7,10 days). Survival of E. crypticus was determined, and sand, filtered sand solution and E. crypticus were analyzed for total Ag. Ag mostly adsorbed to the sand, with strongest sorption found for ionic Ag and PVP-coated AgNPs. Citrate-coated AgNPs gave much higher Ag concentrations in the solution than other two Ag compounds. However, the LC50 was also higher for citrate-coated AgNPs, so it was less toxic. Accumulation of Ag was observed depending on time and external concentration. For all compounds, the LC50 decreased with time and reached steady state after 7 days of exposure. However, LC50 calculated based on internal Ag concentrations in the enchytraeids were constant over time and could be considered more representative of toxicity regardless of time. Survival and reproduction toxicity of AgNPs and AgNO3 to E. crypticus were determined in three different standard soils, namely Lufa 2.2, Lufa 2.3 and Lufa 5M. The standard ISO (2004) guideline 16387 was used for the toxicity tests. Effects on enchytraeid survival were observed at concentrations higher than 500 mg Ag/kg dry soil for the AgNPs, while AgNO3 was more toxic. Reproduction was more sensitive than survival and there was no significant difference in toxicity between AgNPs and AgNO3. Toxicity decreased with increasing soil organic matter content, but not by soil pH. An ERA approach for ENPs was proposed with using analytical hierarchy process (AHP) and fuzzy inference tools. Risk of ENPs were based on the occurrence likelihood (OL), exposure potential (EP) and toxic effects (TE). According to the principles of AHP, sub-factors that are related with OL, EP and TE were determined systematically and a hierarchical structure was developed considering the placing of comparable factors at the same level. A fuzzy scale was proposed to score the factors in the hierarchy using expert judgement. Then overall scores were calculated with a weight-average method and converted to standard trapezoidal numbers. Fuzzy sets corresponding to the overall scores were determined using the proposed scoring scale. OL, EP and TE were combined with a fuzzy inference rule base using expert judgement to obtain the risk magnitude and the risk class based on the scale proposed. Three case studies were analyzed to demonstrate the applicability of the method. The case studies showed that this approach can provide more informative results since it gives the risk class which helps identifying the required risk management strategy. Moreover, the priority weights of the factors may give a clue about research needs or may help identifying which factor should be focused on to reduce the risk.